1976 Fleetwood Vibration/Shudder

[fellenzer]

Is there anything in the differential/drive shaft that could cause a consistent mild shudder or vibration at 40 mph? Also, occasionally while turning at slow speeds? New tires have been balanced three times. Thanks.

[Mike Josephic CLC #3877]

Generally, a "shudder" or vibration at 40 mph would
not indicate tires.

Could it be drivetrain related?  Yes, but nothing specific
comes to mind for me.

Have you checked your brakes lately?  A brake shoe or
caliper that's hanging up could cause a vibration.  I once
had an odd lower speed vibration that several mechanics
were stumped on (1981 Olds Toronado).

I took a ride together with one guy and we noticed that
the vibration varied with light application of the brakes.
Turns out that the parking brake cable was sticking and
sometimes letting the rear brake shoes ride against the
drums.  It really shook the car!!

Mike

[35-709]

Check your motor and tranny mounts.

[fellenzer]

Thanks. Brakes have all been checked. It goes back to the shop on Thursday so I'm looking for anything to have them check.

The vibration/shudder is nominal. It isn't alarming but it is annoying.

Car only has 30K on the clock; however, it is 42 years old and I know it sat outside for a number of years.

A friend suggested it might have something to do with the limited slip differential not having the correct additive. Not exactly sure what he meant.

[Dave Shepherd]

To properly diagnose the many possibilities here, a capable tech needs to drive  it and check it over.

[fellenzer]

The problem is that it isn't always consistent. The 40 mph is now pretty consistent. Happening while turning isn't. That's why I'm asking if anyone has had a similar experience. If it doesn't do it while they have it . . .

[TJ Hopland]

76 still has the CV joints on the driveshaft doesn't it?   If so that is 8 U joints that could have issues.   Does a Fleetwood have a carrier bearing on the shaft?   Or was that just the CC and Limo? 

The limited slip stuff usually doesn't do anything unless there is a difference between the 2 sides.  Are the rear tires a matched set and inflated the same? 

Have you paid attention to the number of wheel weights and locations they have been putting on each time?    A lot of weights in one spot could be a sign of a funky tire.   If the next attempt its a completely different assortment of weights that points to either really unusual problems or a problem with the tire tech and/or equipment.  Something I rarely see done is for the tech to finish the balance, take it off the machine then put it back on and re check.   In theory it should still be balanced.   If its not it wasn't sitting on the machine correctly or there is a problem with the machine.